U.S. patent number 7,615,516 [Application Number 11/334,164] was granted by the patent office on 2009-11-10 for microemulsion containing oil field chemicals useful for oil and gas field applications.
This patent grant is currently assigned to Baker Hughes Incorporated. Invention is credited to Vladimir Jovancicevic, Jiang Yang.
United States Patent |
7,615,516 |
Yang , et al. |
November 10, 2009 |
Microemulsion containing oil field chemicals useful for oil and gas
field applications
Abstract
Useful microemulsions have corrosion inhibitors in the internal
phase and an external phase and at least one surfactant that helps
define the emulsion. The corrosion inhibitor itself may have its pH
adjusted so that it also serves the role of surfactant. The
corrosion inhibitors form microemulsions with particle or droplet
diameters of about 10 to about 300 nm. The microemulsions may be
oil-in-water, water-in-oil or bi-continuous.
Inventors: |
Yang; Jiang (Missouri City,
TX), Jovancicevic; Vladimir (Richmond, TX) |
Assignee: |
Baker Hughes Incorporated
(Houston, TX)
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Family
ID: |
36692821 |
Appl.
No.: |
11/334,164 |
Filed: |
January 18, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060166835 A1 |
Jul 27, 2006 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60645684 |
Jan 21, 2005 |
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Current U.S.
Class: |
507/90; 507/203;
166/305.1 |
Current CPC
Class: |
C09K
8/26 (20130101); C09K 8/36 (20130101); C09K
8/54 (20130101); C09K 8/536 (20130101); C09K
8/52 (20130101) |
Current International
Class: |
C09K
8/524 (20060101); C09K 8/68 (20060101); E21B
43/16 (20060101) |
Field of
Search: |
;507/90,203
;166/305.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
T N. C. Dantas, et al., "Microemulsion System as a Steel Corrosion
Inhibitor," Corrosion, Sep. 2002, pp. 723-727, vol. 58, No. 9, NACE
International. cited by other .
J. Paktinat, et al., "Microemulsion Reduces Adsorption and Emulsion
Tendencies in Bradford and Speechley Sandstone Formations," SPE
93270, 2005 SPE International Symposium on Oilfield Chemistry, Feb.
2-4, 2005, Houston, Texas. cited by other .
G. Penny, et al., "The Application of Microemulsion Additives in
Drilling and Stimulation Results in Enhanced Gas Production," SPE
94274, 2005 SPE Production and Operations Symposium, Apr. 17-19,
2005, Oklahoma City, Oklahoma. cited by other .
PCT International Search Report for International Application No.
PCT/US06/01746, Oct. 3, 2006. cited by other.
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Primary Examiner: Kugel; Timothy J
Attorney, Agent or Firm: Mossman Kumar & Tyler PC
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional Patent
Application No. 60/645,684 filed Jan. 21, 2005.
Claims
What is claimed is:
1. A method of adding an oil field chemical to a fluid comprising:
providing a fluid selected from the group consisting of water;
mixtures of hydrocarbons and water; mixtures of hydrocarbons, water
and gas; mixtures of hydrocarbons, water and solids; mixtures of
hydrocarbons, water, gas and solids; mixtures of water, gas, and
solids; and mixtures of water and solids; introducing an oil field
chemical-containing microemulsion to the fluid, where the oil field
chemical-containing microemulsion comprises: a non-aqueous internal
phase comprising the oil field chemical, where the oil field
chemical additionally has a surfactant property and the oil field
chemical is present in an amount effective to form a stable
microemulsion of droplets of the internal phase in the external
phase; and an aqueous external phase; and breaking the
microemulsion to add the oil field chemical to the fluid.
2. The method of claim 1 where the fluid is in a well and little or
no fluid is present in a subterranean formation.
3. The method of claim 2 further comprising producing the fluid
from a well.
4. The method of claim 1 where the oil field chemical is selected
from the group consisting of: acidic oil field chemicals to which
sufficient base has been added to impart surfactant property
thereto; and basic oil field chemicals to which sufficient acid has
been added to impart surfactant property thereto; and mixtures
thereof.
5. The method of claim 1 where the external phase comprises water
and the internal phase further comprises a co-solvent selected from
the group of branched or straight-chain alcohols, glycols and alkyl
glycol ethers having from 3 to 8 carbon atoms.
6. The method of claim 1 where the microemulsion comprises: about 1
to about 90 wt % oil field chemical; and about 10 to about 99 wt %
water.
7. The method of claim 1 where the microemulsion further comprises
an additional oil field chemical and the internal phase comprising
the oil field chemical are separate droplets from the internal
phase comprising the additional oil field chemical.
8. The method of claim 1 where the concentration of the
microemulsion in the fluid ranges from about 1 to about 4000
ppm.
9. The method of claim 1 where the microemulsion is continuously
injected into the fluid.
10. The method of claim 1 where the oil field chemical that is a
corrosion inhibitor is selected from the group consisting of
aliphatic amines, saturated and unsaturated fatty acids,
alkanolamides, alkyl phosphate esters, thiophosphate esters,
imidazolines, sulfur-containing inhibitors, and mixtures
thereof.
11. The method of claim 1 further comprising transporting the fluid
through a conduit.
12. A method of adding an oil field chemical to a fluid comprising:
providing a fluid selected from the group consisting of water;
mixtures of hydrocarbons and water; mixtures of hydrocarbons, water
and gas; mixtures of hydrocarbons, water and solids; mixtures of
hydrocarbons, water, gas and solids; mixtures of water, gas, and
solids; and mixtures of water and solids; introducing an oil field
chemical-containing microemulsion to the fluid, where the oil field
chemical-containing microemulsion comprises: a non-aqueous internal
phase comprising the oil field chemical; an aqueous external phase;
and at least one surfactant of a kind and amount effective to form
a stable microemulsion of droplets of the internal phase in the
external phase; and breaking the microemulsion to add the oil field
chemical to the fluid.
13. The method of claim 12 where the fluid is in a well and little
or no fluid is present in a subterranean formation.
14. The method of claim 13 further comprising producing the fluid
from a well.
15. The method of claim 12 where the external phase comprises water
and the internal phase further comprises a co-solvent selected from
the group of branched or straight-chain alcohols, glycols and alkyl
glycol ethers having from 3 to 8 carbon atoms.
16. The method of claim 12 where the microemulsion comprises: about
1 to about 90 wt % oil field chemical; about 5 to about 96% water;
and about 0.2 to about 50 wt % total surfactant.
17. The method of claim 12 where the oil field chemical is selected
from the group consisting of corrosion inhibitors, corrosion
products removers, asphaltene inhibitors, scale inhibitors, scale
dissolvers, paraffin inhibitors, gas hydrate inhibitors, biocides,
pH modifiers, metal chelators, metal complexors, antioxidants,
wetting agents, clay stabilizers, wax inhibitors, wax dissolvers,
wax dispersants, H.sub.2S scavengers, waterflow inhibitors, sand
consolidation additives, permeability modifiers, foaming agents,
microorganisms, nutrients for microorganisms, salts, polymers,
polymer stabilizers, crosslinkers, and breakers.
18. The method of claim 12 where the microemulsion further
comprises an additional oil field chemical and the internal phase
comprising the oil field chemical are separate droplets from the
internal phase comprising the additional oil field chemical.
19. The method of claim 12 where the concentration of the
microemulsion in the fluid ranges from about 1 to about 4000
ppm.
20. The method of claim 12 where the microemulsion is continuously
injected into the fluid.
21. The method of claim 12 further comprising transporting the
fluid through a conduit.
22. A method of improving the corrosion inhibition of a fluid
comprising: providing a fluid selected from the group consisting of
water; mixtures of hydrocarbons and water; mixtures of
hydrocarbons, water and gas; mixtures of hydrocarbons, water and
solids; mixtures of hydrocarbons, water, gas and solids; mixtures
of water, gas, and solids; and mixtures of water and solids;
introducing a corrosion inhibitor-containing microemulsion to the
fluid in an amount effective to improve the corrosion inhibition
thereof, where the corrosion inhibitor-containing microemulsion
comprises: a non-aqueous internal phase comprising a corrosion
inhibitor; an aqueous external phase; and at least one surfactant
of a kind and amount effective to form a stable microemulsion of
droplets of the internal phase in the external phase; and breaking
the microemulsion to add the corrosion inhibitor to the fluid;
where the corrosion inhibition of the fluid is increased as
compared with an identical method except that the corrosion
inhibitor is not added in a microemulsion but is instead added
directly or in an emulsion that is not a microemulsion.
23. The method of claim 22 where the microemulsion further
comprises an additional oil field chemical selected from the group
consisting of corrosion products removers, asphaltene inhibitors,
scale inhibitors, scale dissolvers, paraffin inhibitors, gas
hydrate inhibitors, biocides, pH modifiers, metal chelators, metal
complexors, antioxidants, wetting agents, clay stabilizers, wax
inhibitors, wax dissolvers, wax dispersants, H.sub.2S scavengers,
waterflow inhibitors, sand consolidation additives, permeability
modifiers, foaming agents, microorganisms, nutrients for
microorganisms, salts, polymers, polymer stabilizers, crosslinkers,
and breakers.
24. The method of claim 23 where the internal phase comprising the
corrosion inhibitor are separate droplets from the internal phase
comprising the additional chemical.
25. The method of claim 22 where the fluid is in a well and little
or no fluid is present in a subterranean formation.
26. The method of claim 25 further comprising producing the fluid
from a well.
27. The method of claim 22 where the external phase comprises water
and the internal phase further comprises a co-solvent selected from
the group of branched or straight-chain alcohols, glycols and alkyl
glycol ethers having from 3 to 8 carbon atoms.
28. The method of claim 22 where the microemulsion comprises: about
1 to about 90 wt % corrosion inhibitor; about 5 to about 96% water;
and about 0.2 to about 50 wt % total surfactant.
29. The method of claim 22 where the concentration of the
microemulsion in the fluid ranges from about 1 to about 4000
ppm.
30. The method of claim 22 where the microemulsion is continuously
injected into the fluid.
31. The method of claim 22 where the corrosion inhibitor is
selected from the group consisting of consisting of aliphatic
amines, saturated and unsaturated fatty acids, alkanolamides, alkyl
phosphate esters, thiophosphate esters, imidazolines,
sulfur-containing inhibitors, and mixtures thereof.
32. The method of claim 22 further comprising transporting the
fluid through a conduit.
33. The method of claim 22 where corrosion inhibition is greater
when the corrosion inhibitor is introduced in the microemulsion as
compared to corrosion inhibition obtained where the same corrosion
inhibitor is introduced in the same amount without a microemulsion.
Description
TECHNICAL FIELD
The invention relates to the use of corrosion inhibitors in oil and
gas field applications, and most particularly relates, in one
non-limiting embodiment, to using microemulsions to deliver
corrosion inhibitors in oil and gas field applications.
BACKGROUND
It is well known that steel tubulars and equipment used in the
production of oil and gas are exposed to corrosive environments.
Such environments generally consist of acid gases (CO.sub.2 and
H.sub.2S) and brines of various salinities. Under such conditions
the steel will corrode, possibly leading to equipment failures,
injuries, environmental damage and economic loss. Further in some
cases, drilling fluids have acid intentionally added thereto in
order to acidize the formations to enhance hydrocarbon recovery.
This added acid also causes corrosion problems.
While the rate at which corrosion will occur depends on a number of
factors such as metallurgy, chemical nature of the corrosive agent,
salinity, pH, temperature, etc., some sort of corrosion almost
inevitably occurs. One way to mitigate this problem consists of
using corrosion inhibitors in the hydrocarbon production
system.
Corrosion inhibitors are widely used in oil and gas production
wells and pipeline transmission lines. The corrosion inhibitors are
generally high viscosity liquids. In order to form a pumpable
product, a solvent is usually used to dilute the inhibitors and
form a relatively low viscosity fluid. In general, the use of a
large amount of solvent is undesirable since it increases the
product cost and may contribute to flammability.
It is known that the corrosion of iron and steel alloys in contact
with oil-in-brine emulsions can be inhibited by treating the
emulsions with a water soluble polymer, specifically water soluble
anionic, non-ionic and cationic polymers and/or nitrogen-containing
corrosion inhibitors.
A microemulsion is a thermodynamically stable fluid. It is
different from kinetically stable emulsions which will be break
into oil and water over time. Water-in-oil microemulsions have been
known to deliver water soluble oil field chemicals into
subterranean rock formations. Also known are oil-in-alcohol
microemulsions containing corrosion inhibitors in anti-freeze
compositions.
It would be advantageous if a new corrosion inhibitor were
discovered that would be an improvement over the presently known
systems. It is always desirable to produce greater corrosion
inhibiting ability using less corrosion inhibiting material and/or
less inert material, particularly if the inert material is
relatively expensive. It would also be useful if the corrosion
inhibitor was stable during storage and reduced in flammability as
compared with conventional corrosion inhibitors.
SUMMARY
In carrying out these and other objects of the invention, there is
provided, in one form, a method of adding an oil field chemical to
a fluid that involves providing a fluid including, but not
necessarily limited to, water; mixtures of hydrocarbons and water;
mixtures of hydrocarbons, water and gas; mixtures of hydrocarbons,
water and solids; mixtures of hydrocarbons, water, gas and solids;
mixtures of water, gas, and solids; and mixtures of water and
solids. An oil field chemical-containing microemulsion is
introduced to the fluid. The oil field chemical-containing
microemulsion includes a non-aqueous internal phase that contains
the oil field chemical, where the oil field chemical additionally
has a surfactant property and the oil field chemical is present in
an amount effective to form a stable microemulsion of droplets of
the internal phase in the external phase. The microemulsion
additionally includes an aqueous external phase.
Alternatively, the a non-aqueous internal phase includes the oil
field chemical; an aqueous external phase; and at least one
surfactant of a kind and amount effective to form a stable
microemulsion of droplets of the internal phase in the external
phase. The surfactant is discrete and separate from the oil field
chemical.
There is also provided, in another non-restrictive form, a method
of improving the corrosion inhibition of a fluid that may be water;
mixtures of hydrocarbons and water; mixtures of hydrocarbons, water
and gas; mixtures of hydrocarbons, water and solids; mixtures of
hydrocarbons, water, gas and solids; mixtures of water, gas, and
solids; and mixtures of water and solids. The method additionally
involves introducing a corrosion inhibitor-containing microemulsion
to the fluid in an amount effective to improve the corrosion
inhibition thereof. The corrosion inhibitor-containing
microemulsion includes an internal phase including a corrosion
inhibitor, an external phase and at least one surfactant of a kind
and amount effective to form a stable microemulsion of internal
phase droplets in the external phase.
DETAILED DESCRIPTION
It has been discovered that microemulsions can be used to
"solubilize" or deliver oil-soluble oil field chemicals, e.g.
corrosion inhibitors, using less organic or non-aqueous solvent.
The microemulsion also increases the dispersibility of oil field
chemicals into the produced fluids, pumped fluids, and the like,
thus increasing the performance of the chemical. In addition, the
compositions and methods herein may additionally or alternatively
incorporate other oil field chemicals such as corrosion products
removers, asphaltene inhibitors, scale inhibitors, scale
dissolvers, paraffin inhibitors, gas hydrate inhibitors, biocides,
pH modifiers, metal chelators, metal complexors, antioxidants,
wetting agents, clay stabilizers, wax inhibitors, wax dissolvers,
wax dispersants, H.sub.2S scavengers, waterflow inhibitors, sand
consolidation additives, permeability modifiers, foaming agents,
microorganisms, nutrients for microorganisms, salts, polymers,
polymer stabilizers, crosslinkers, and breakers. These oil field
chemicals may exist in oil-soluble (non-aqueous) and/or
water-soluble (aqueous) forms. If these other oil field chemicals
are incompatible with the corrosion inhibitors, they may be
incorporated into different droplets or particles and subsequently
mixed in a procedure including, but not necessarily limited to
mixing them prior to introduction into the fluid. Alternatively,
the other oil field chemicals may be present in the other
phase.
It will also be appreciated that the methods and compositions
herein are not limited to the case where the oil field chemical is
oil soluble. The microemulsion may be designed in such a way that
the internal phase is water which contains a water-soluble oil
field chemical and the external phase is non-aqueous.
It will be appreciated that although the methods and compositions
are often discussed herein for the embodiment where the oil field
chemical is a corrosion inhibitor, the methods and compositions may
be adapted to deliver, inject, provide and otherwise introduce a
different oil field chemical. Many oil and gas production and flow
lines contain significant levels of water in the liquid phase. As
previously noted, such lines may be in danger of corrosion.
Suitable fluids to which the compositions and methods herein may be
applied include, but are not necessarily limited to, water;
mixtures of hydrocarbons and water; mixtures of hydrocarbons, water
and gas; mixtures of hydrocarbons, water and solids; mixtures of
hydrocarbons, water, gas and solids; mixtures of water, gas, and
solids; and mixtures of water and solids. Hydrocarbon systems may
also be defined herein as any liquid system that has at least 0.5%
of hydrocarbon component in it. Hydrocarbon systems include, but
are not necessarily limited to, multiphase flowlines and vessels
(for example oil/water, oil/water/gas) in oil and gas production
systems. It will be appreciated that by the term "hydrocarbon
fluid", it is expected that oxygenated or nitrogenated hydrocarbons
such as lower alcohols, glycols, amines, ethers, and the like may
be included within the definition. The term "hydrocarbon fluid"
also means any fluid that contains hydrocarbons, as defined herein
to also include oxygenated hydrocarbons. Thus, multiphase
hydrocarbon-containing systems (e.g. oil/water, oil/water/gas),
such as oil and gas production flowlines are primary applications
for this technology.
In general, microemulsions are known in the art, and are known to
be fundamentally different from regular emulsions. Microemulsions
are thermodynamically stable systems. In one non-limiting
embodiment, the particle size of microemulsions ranges from about
10 nm to about 300 nm. In a different non-restrictive embodiment,
the particle size of the microemulsion is not particularly
important as long as the emulsion is a thermodynamically stable
one--a distinguishing characteristic of microemulsions.
Microemulsions typically appear as clear or translucent solutions.
The particle sizes of microemulsions may be identified by dynamic
light scattering or neutron scattering or other suitable technique.
Because of the small particle sizes, microemulsions appear as clear
or translucent solutions. Microemulsions have ultralow interfacial
tension between the water phase and the oil phase or non-aqueous
phase.
As noted, microemulsions increase the dispersibility of the oil
field chemical (e.g. a corrosion inhibitor) into fluids, such as
dispersed fluids, and thus increase the performance of the oil
field chemical (e.g. inhibitor). Microemulsions may also
incorporate other incompatible oil-soluble oilfield chemicals and
water-soluble oil-field chemicals as alternatives to or additions
to the one initially used. For instance, the oil-soluble oilfield
chemical such as a corrosion inhibitor may be in the internal
phase, whereas the water-soluble scale inhibitor may be in the
aqueous external phase.
In further detail, the microemulsion herein contains or includes an
oil field chemical, at least one surfactant and water, where in one
non-limiting embodiment an external phase is aqueous and an
internal phase is non-aqueous. Alternatively, the microemulsion can
either be water-in-oil or a bi-continuous microemulsion. It will be
appreciated that a bi-continuous microemulsion does not strictly
have an internal phase or an external phase. As such, a
bi-continuous microemulsion does not necessarily have particles,
although it may have both aqueous particles in the non-aqueous
portion along with non-aqueous particles inside an aqueous portion,
where the aqueous and non-aqueous regions occasionally become
discontinuous. It will be appreciated that the microemulsions
herein will be most commonly described in terms of a non-aqueous
internal phase and an aqueous external phase, primarily because
many known corrosion inhibitors are generally oil-soluble, but the
micro-emulsions herein are not limited to these particular
embodiments.
The compositions herein may also include a co-solvent or oil when
it is necessary to form such microemulsions. The oil field chemical
itself may act as the oil phase or as the surfactant per se
depending upon its solubility, as will be described in more detail
below.
In another non-restrictive embodiment, a microemulsion may have
proportions of from about 1 to about 90 wt % oil field chemical,
from about 5 to about 96% water, and about 0.2 to about 50 wt %
total surfactant. In another non-limiting embodiment, the
proportions may range from about 1 to about 95 wt % oil field
chemical, from about 3 to about 98% water, and about 0.1 to about
50 wt % total surfactant. In the case where the oil field chemical
also serves the role of the surfactant, the microemulsion may
include from about 1 to about 90 wt % oil field chemical and from
about 10 to about 99 wt % water.
Suitable corrosion inhibitors to be used with the microemulsions
herein may be any or most known corrosion inhibitors, and likely
those to be developed in the future. Such corrosion inhibitors
include, but are not necessarily limited to, alkanolamides, alkyl
phosphate esters, thiophosphate esters, fatty acids such as alkyl
dimeric acids, maleated fatty acids, imidazolines,
sulfur-containing inhibitors, and the like. The alkyl chain lengths
may range from 8 to 24 carbon atoms. In one non-limiting
embodiment, an unsaturated chain such as oleyl may be used. Other
examples of corrosion inhibitors are compounds for inhibiting
corrosion on steel, especially under anaerobic conditions, and may
especially be film formers capable of being deposited as a film on
a metal surface e.g. a steel surface such as a pipe-line wall. Such
compounds may be non-quaternized long aliphatic chain hydrocarbyl
N-heterocyclic compounds, where the aliphatic hydrocarbyl group may
have from 5 to 12 or more carbon atoms; mono- or di-ethylenically
unsaturated aliphatic groups e.g. of 8-24 carbons such as oleyl,
etc. The N-heterocyclic group can have 1-3 ring nitrogen atoms with
5-7 ring atoms in each ring; imidazole and imidazoline rings are
suitable in one non-limiting embodiment. The ring may also have an
aminoalkyl e.g. 2-aminoethyl and/or hydroxyalkyl e.g.
2-hydroxyethyl substituents.
Suitable scale inhibitors include those effective in stopping
calcium and/or barium scale with threshold amounts rather than
stoichiometric amounts. Acceptable scale inhibitors include, but
are not necessarily limited to, water-soluble organic molecules
with at least 2 carboxylic and/or phosphonic acid and/or sulphonic
acid groups, e.g. 2-30 such groups. In another non-restrictive
version, the scale inhibitor may be an oligomer or a polymer, or
may be a monomer with at least one hydroxyl group and/or amino
nitrogen atom, especially in a hydroxycarboxylic acid or hydroxy or
aminophosphonic, or sulphonic acid. The inhibitor may be used
primarily for inhibiting calcium and/or barium scale, but other
scales may also be prevented. Non-limiting examples of such
compounds used as inhibitors are aliphatic phosphonic acids with
2-50 carbons, such as hydroxyethyl diphosphonic acid, and
aminoalkyl phosphonic acids, e.g. polyaminomethylene phosphonates
with 2-10 N atoms, e.g. each bearing at least one methylene
phosphonic acid group; examples of the latter include, but are not
limited to, ethylenediamine tetra-(methylene phosphonate),
diethylenetriamine penta(methylene phosphonate) and the triamine-
and tetramine-polymethylene phosphonates with 2-4 methylene groups
between each N atom, at least 2 of the numbers of methylene groups
in each phosphonate being different. Other scale inhibitors include
polycarboxylic acids such as acrylic, maleic, lactic or tartaric
acids, and polymeric anionic compounds such as polyvinyl sulphonic
acid and poly(meth)acrylic acids, optionally with at least some
phosphonyl or phosphinyl groups as in phosphinyl polyacrylates. The
scale inhibitors are suitably at least partly in the form of their
alkali metal salts e.g. sodium salts, in some non-limiting
embodiments.
In one non-restrictive version, suitable asphaltene inhibitors
include, but are not limited to, amphoteric fatty acids or salts of
an alkyl succinate, while suitable wax inhibitors include, but are
not limited to, a polymer such as an olefin polymer e.g.
polyethylene or a copolymeric ester, e.g. ethylene-vinyl acetate
copolymer, and suitable wax dispersants include, but are not
limited to, polyamides. Suitable hydrogen sulfide scavengers
include, but are not limited to, oxidants, such as inorganic
peroxides, e.g. sodium peroxide, or chlorine dioxide, or an
aldehyde, e.g. of 1-10 carbons such as formaldehyde or
glutaraldehyde or (meth)acrolein. Appropriate gas hydrate
inhibitors include, but are not limited to, solid polar compounds,
which may be polyoxyalkylene compounds or alkanolamides, or
tyrosine or phenylalanine.
In another non-restrictive embodiment, the amount of oil field
chemical used is in the range from 1-50% w/w of the non-aqueous
phase, suitably from 5-40% w/w, alternatively from 6-30% w/w.
Within these ranges the amount used would depend upon the nature of
the chemical used and its intended purpose.
In one non-limiting embodiment, the surfactant may be the corrosion
inhibitor per se with an adjusted pH to give the necessary
microemulsion-forming characteristics. In a non-limiting example,
the addition of base to increase pH will convert a fatty acid into
a surfactant-soap. Further and alternatively, the addition of acid
will protonate an amine and make it water-soluble. It should be
understood that not all oil field chemicals need to have their pH
adjusted to impart sufficient surfactant properties necessary to
create a microemulsion, i.e. they may naturally possess such
surfactant characteristics.
Conventional surfactants such as anionic, nonionic, cationic and
amphoteric surfactants may also be used. Suitable anionic
surfactants include, but are not necessarily limited to, alkyl
sulfates, sulfonates, sulfosuccinates, phosphates, alkyl benzene
sulfonates and the like. Other suitable anionic surfactants
include, but are not necessarily limited to, fatty carboxylates,
alkyl sarcosinates, alkyl phosphates, alkyl sulfonates, alkyl
sulfates and the like and mixtures thereof. The alkyl chain length
on the surfactants may range from 8 to 24 carbon atoms.
Suitable nonionic surfactants include, but are not necessarily
limited to, alkoxylated alcohols or ethers, alkyl ethoxylates,
alkylamido ethoxylates, alkylamine ethoxylates, alkyl glucosides,
alkoxylated carboxylic acids, sorbitan derivatives, again where the
alkyl chain length may range from 8 to 24 carbon atoms. More
specific examples include, but are not necessarily limited to
nonylphenol ethoxylate-3, alkyl ethoxylates-3, oleyl carboxylic
diethylamides, and the like and mixtures thereof.
Suitable surfactants and mixtures thereof include, but are not
necessarily limited to, cationic surfactants such as, monoalkyl
quatemary amines, such as cocotrimethylammonium chloride,
cetyltrimethylammonium chloride, stearyltrimethylammonium chloride,
soyatrimethylammonium chloride, behentrimethylammonium chloride,
and the like and mixtures thereof. Other suitable cationic
surfactants that may be useful include, but are not necessarily
limited to, dialkylquaternary amines such as
dicetyldimethylammonium chloride, dicocodimethylammonium chloride,
distearyldimethylammonium chloride, and the like and mixtures
thereof.
The amphoteric/zwitterionic surfactants that may be useful include,
but are not necessarily limited to, alkyl betaines, alkylamido
propyl betaines, alkylampho acetates, alkylamphopropionates,
alkylamidopropyl hydroxysultaines and the like and mixtures
thereof.
Optional co-solvents include, but are not necessarily limited to
alcohols, glycols, fatty alcohols, alkyl glycol ethers with chain
lengths from 3 to 8 carbon atoms, where the chains may be straight
or branched. In one non-limiting embodiment, the chain length may
be from 4 to 6. Specific examples of suitable co-solvents include,
but are not necessarily limited to, isopropanol, butanol, pentanol,
hexanol, butyl monoglycol ether, butyl diglycol ether, and the like
and mixtures thereof.
Solvents optionally used in the hydrocarbon internal phase may
include, but not necessarily be limited to, mineral oil, mineral
spirits, or other combinations of straight, branched, alicyclic, or
aromatic hydrocarbons. In one non-limiting embodiment of the
invention, the hydrocarbons in the external phase have from about 7
to about 18 carbon atoms.
The microemulsions discussed herein may be readily made by
combining the various components and applying mixing, agitation or
turbulence until a suitable microemulsion is formed.
As noted, the microemulsions may also include other oil field
chemicals including, but not necessarily limited to, asphaltene
inhibitors, scale inhibitors, paraffin inhibitors and hydrate
inhibitors, etc.
Additionally, the microemulsions with oil field chemicals may be
used in batch treatments or introduced by continuous injection,
such as through capillary injection. Further, the microemulsions
may be used in umbilical applications to subsea pipelines. The
product may also be introduced into the well by batching the
product down the tubing either in a procedure known as "batch and
fall" or by tubing displacement. These microemulsion formulations
are expected to be higher performance and of lower cost than
conventional pure solvent-based oil field chemicals, since solvents
are more expensive than water. It is also expected that these
microemulsion oil field chemicals will be more environmentally
friendly since less solvent is used. These microemulsions should
also have the benefit of having a lower flash point since less
solvent is present. In addition, concentrated products may be
formulated with mutually incompatible and/or synergistic
intermediates.
It is difficult to predict in advance what an effective use
concentration should be because such concentration is dependent
upon many interrelated variables in the system being treated,
including, but not necessarily limited to, the nature of the fluid,
the temperature of the fluid, the nature of the oil field
chemicals, the nature of the surfactant, etc. Nevertheless, to give
some sense of typical concentrations, one non-limiting effective
use concentration range of the microemulsion in the fluid is 1 to
4000 ppm as product in the fluid. In another non-limiting
embodiment of the invention, the lower threshold of the
concentration range is at about 30 ppm, where the upper threshold
of the concentration range may be up to about 1000 ppm, or 500 ppm,
alternatively up to 100 ppm of microemulsion product based on the
total fluid treated.
It is expected that in one non-limiting embodiment the
microemulsion is broken and/or inverted to deliver the corrosion
inhibitor to the pipeline, production system, or other equipment
desired to be protected. The microemulsions may be broken or
inverted by a variety of mechanisms, such as by chemical or
temperature means, but one common way is expected to be simple
dilution. Methods for destabilizing or breaking the microemulsion
include, but are not necessarily limited to, a change in
temperature, a change in pH, a change in salinity, a change in
alcohol concentration, a change in stabilizing surfactant
concentration, a change in organic ion concentration, a change in
destabilizing surfactant concentration, a change in surfactant
adsorbent material concentration, an ultrasonic pulse, and an
electrical field, and combinations thereof.
To further illustrate the invention, the compositions and methods
herein will be additionally described by way of the following
non-limiting Examples, which are intended only to further show
specific embodiments of the invention, but not to limit it in any
way.
EXAMPLE 1
One embodiment of the oil-in-water microemulsion containing
corrosion inhibitor has the following composition: 2 wt % toluene 4
wt % oleic imidazoline (corrosion inhibitor) 4 wt % oleic acid
(corrosion inhibitor) 2 wt % dodecylbenzene sulfonic acid 2 wt %
ethanolamine 20 wt % butyl alcohol 66 wt % water
The above ingredients were blended in sequence. A clear and stable
microemulsion was obtained. The resulting oil-in-water
microemulsion was easily diluted to the water phase.
EXAMPLE 2
One embodiment of a water-in-oil microemulsion containing corrosion
inhibitor has the following composition: 16 wt % oleic imidazoline
(corrosion inhibitor) 16 wt % oleic acid (corrosion inhibitor) 8 wt
% dodecylbenzene sulfonic acid 5 wt % ethanolamine 11 wt % butyl
alcohol 33 wt % toluene 11 wt % water
The above ingredients were blended in sequence. A clear and stable
microemulsion was obtained. The resulting water-in-oil
microemulsion was easily dissolved a hydrocarbon solvent.
EXAMPLE 3
Copper displacement tests were run with 30 ppm corrosion inhibitor
in NACE/Isopar M as a 90/10 mixture with CO.sub.2 purged at
60.degree. C. for 5 hours, then dipped into 10% CuSO.sub.4
solution. The results presented in Table I demonstrate that the
corrosion inhibitor in microemulsion has better coverage than that
of the same corrosion inhibitor in the same amount delivered as a
conventional oil based corrosion inhibitor. This difference was
determined by a visual inspection of the coupons. The improvement
was visually noticeable.
TABLE-US-00001 TABLE I Conventional oil soluble corrosion inhibitor
Microemulsion corrosion inhibitor Component Wt % Component Wt %
Oleyl imidazoline amide 5.0 Oleyl imidazoline amide 5.0 Oleic acid
3.0 Oleic acid 3.0 Oleyl imidazoline 3.0 Oleyl imidazoline 3.0
Nonylphenol ethoxylate 2.0 Nonylphenol ethoxylate 2.0 phosphate
phosphate Aromatic solvent 87.0 Butanol 15.0 Nonyl phenol
ethoxylate-10 3.0 Glacial acetic acid 4.0 Water 65.0
EXAMPLE 4
Other oilfield chemicals can be also included together with a
corrosion inhibitor, such as scale inhibitor (e.g.
1-hydroxyethanediphosphonic acid). The formula given below (wt %)
was demonstrated as a microemulsion:
TABLE-US-00002 Oleyl imidazoline 12% Oleic acid 2% Glacial acetic
acid 4% Nonyl phenol ethoxylate-10 4% Butanol 14%
1-Hydroxyethanediphosphonic acid 10% Water 54%
Many modifications may be made in the composition and
implementation of this invention without departing from the spirit
and scope thereof that are defined only in the appended claims. For
example, the microemulsions may be different from those explicitly
used and described here. Additionally, oil field chemicals or
additives, e.g. corrosion inhibitors, among others, surfactants,
optional solvents, etc. other than those specifically mentioned may
find utility in the methods and compositions of this invention.
Various combinations of water, corrosion inhibitors and
surfactants, besides those explicitly mentioned herein, and in
different proportions than those mentioned herein, are also
expected to find use as effective and improved microemulsions.
* * * * *